A film is made interesting through the change that is depicted in it, which is usually presented by the change of the protagonist. Presenting change is based on fairytales, legends and stories. People are interested in "the small and the helpless growing into a hero or a winner".
In the beginning of the 1900's Vladimir Propp researched Russian folklore and found in them the same archetypes and plots over and over again. Propp's ideas, developed by folklorists and anthropologists, finally reached Hollywood, where Christopher Vogler revised and amended screenplays.
Vogler combined Propp's ideas to researcher Joseph Campbell's book "Hero With a Thousand Faces". In this book Campbell describes the hero's -- the main character of each story -- journey through the story. Based on the hero's journey Vogler wrote his own version of the story for Hollywood pictures. The book became quite popular among scriptwriters. The same pattern worked in romantic comedies as well as in adventure films.
The change of the Star Wars protagonist, Luke Skywalker, from a shy youngster into the savior of the universe and a hero, serves as a good example of this change.
Jonathan Young: Joseph Campbell's Mythic Journey. [www.rain.org/~young/
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